Measured-service automatic-telephone-exchange system



Aug. 25, 1925. 1,550,752

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P. C. SMITH MEASURED SERVICE AUTOMATIC TELEPHONE EXCHANGE SYSTEM Filed June 7. 1923 Ill l ll ill Patented Aug. 25, 1925.

UNITED STATES PATENT OFFICE.

PERCY C. SMITH, OF EAST ORANGE, NEW JERSEY, ASSIGNOR T0 WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK,

MEASURED-SERVICE AUTO'MATIC-TELEPHONE-EXCHANGE SYSTEET.

Application filed June '7,

T 0 all whom it may concern:

Be it known that I, PERCY C. SMITH, a citizen of the United States of America, residing at East Orange, in the county of Essex, State of New Jersey, have invented certain new and useful Improvements in Measured Service Automatic Telephone Exchange Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to a telephone system, and more particularly to a system in which connections are established between subscribers lines by means of mechanical switching devices.

Subscribers lines in a telephone exchange system are customarily divided into service groups in accordance with the manner in which the subscribers are to be charged for service, that is, certain of the lines known as flat rate lines are permitted to make any number of calls within the exchange area for a fixed monthly rate and other lines are permitted a fixed number of calls per month at a fixed rate and are charged additionally for all calls in excess of such number. Lines of this latter class are equipped at the central oiiice with individual message registers for registering each successful call in order that the telephone company may be enabled to make an additional charge for all calls in excess of the fixed monthly number. A third class of lines, usually terminating in pay-station booths, are provided with coin boxes in which the calling subscriber is required to deposit a coin or token before obtaining a desired connection, the coin being collected if the call is successful and refunded if it is unsuccessful.

In all exchange areas there are certain lines to which it is desirable and equitable to permit the extension of connections without charging the calling subscribers for service, as by either operating the subscribers message register or collecting a deposited coin or token. Such lines, for example, are lines extending to the commercial oiiices of the telephone company, to fire stations, police stations, hospitals, etc. In exchange areas where all connections are extended manually by operators, it is obvious that the operators can take the necessary stepsto prevent the charging of such free line calls against calling subscribers as by 1923. Serial No. 643,869.

refunding the coin deposited or by preventing the operation of the calling subscribers message register.

In exchange areas in which connections are extended by machine switching mechanism, however, it is necessary to provide some means which will function automatically to give free service on connections to lines of the character above enumerated. This has usually been accomplished heretoforce by the segregation of all lines of a free service character, and by terminating them in the terminal banks of certain final switches, such final switches being arranged to omit the usual service charging operation. In this method of handling calls to free lines it is therefore necessary to reserve an entire frame of switches having terminal facilities for from 100 to 500 lines, depending upon the type of final switch used, whereas the number of such free lines in any given ofiice rarely exceeds 50. It is thus apparent that such final selector switches are not eiiiciently employed and that a great economy in apparatus may be effected by arranging such final switches to function in the usual manner in making connections to regular lines to which service is charged and to function in a different manner to omit the call charging function when connections are established to so-called free lines.

It is therefore the object of the present invention to provide final selector switches which will enable calls to be extended to certain lines without charging the calling subscribers therefor, but will charge subscribers for all other calls established therethrough.

The principal feature of this invention resides in the provision in a final selector switch of the multibrush type of discriminating means for segregating free lines in any brush group and preventing the closure of a metallic talking path back to the incoming selector when a connection is made with any line of such group, whereby the usual reversal of current at the incoming selector when the called subscriber answers is prevented. The talking path under such conditions is established inductively at the final selector switch and the called subscriber is supplied with talking current through the windings of a relay which is bridged across the talking conductors on the brush side of the inductive connection. On calls estab lished to lines terminating in other brush groups, the final selector switch functions in the usual well known manner.

A further feature resides in the provision in a final selector switch of this character of means for further segregating free lines in any tens group of a desired brush group, and inthe manner outlined above preventing call charging when a connection is suc cessfully established with a free line thus segregated.

These and other features of the invention will be apparent from consideration of the following description and the accompanying drawings, in which Fig. 1 shows a subscribers line terminating at the exchange office in a line .switch, and in the lower right portion of the figure a diagrammatic representation of a central ofiice register sender and sender finder switch. liigure 2 shows a district selector switch accessible from the line switch of Fig. 1 and arranged to be controlled by the otiice sender to extend connections from the calling line to the desired district or otiice of the exchange in which the desired line terminates. Fig. 3 shows an incoming selector switch for further extending connections provided with equipment for providing ringing current to all lines and with supervisory apparatus for controlling the charging of successful calls. Fig. 4 shows a final selector switch provided with discrin'iinating apparatus in accordance with the present invention for enabling calls to be extended without charge to certain lines segregated in any number of brush groups thereof. This figure also shows one of the subscribers lines terminating in the bank of the final selector switch. Fig. 5 shows a modification of the final selector switch of Fig. 4, having a further provision for enabling calls to be extended without charge to certain lines segregated in any tens group of brush group. Fig. 6 shows a modification of the commutator of a final selector for enabling segregation of free lines to be readily accomplished. For a more complete disclosure of the invention Figs. 1 to 4, inclusive should be placed in horizontal alignment with Fig. 1 at the left.

In considering the modified form of the invention Fig. 5 should be substituted for Fig. 4.

Description of apparatus and general method of operation.

The line switch, district selector, incoming selector and sender disclosed in Figs. 1 to 8, inclusive, are all substantially of the same type and function in the same manner as the similar apparatus disclosed in the patent to F. A. Stearn and F. J. Scudder, No. 1,395,597 7 issued November 1, 1921, and reference to this patent may be had for a detailed description thereof.

The final selector switch of Fig. 4 is of substantially the same type as disclosed in the aforesaid patent, with the exception of the changes made thereto in accordance with the present invention. These changes comprise the addition of three relays 428, 440 and 445 and the serrated portion 465 of the commutator 455. In general, the final selector functions as follows: During the brush selection movement of the switch, the sequence switch 400 is in position 2, and as the shaft wiper 456 advances into contact with a segment of the commutator 465, which is connected with the commutator a circuit is established for relay 428. Relay 428 locks and opens the metallic connection between brushes 452 and 453 and the tip and ring conductors of the trunk circuit. If only the upper brush group is segregated for free line service, the serrated commutator 465 is severed at 467, as by a saw kerf into the edge of the commutator mounting. If the upper two brush groups are to be segregated, the commutator 465 is severed from the commutator 455 at 468. Under these conditions, when the sequence switch 400 reaches the talking position and the sequence switch of the incoming selector switch 350 reaches the ringing position, slow releasing relay 440 energizes and ringing current passes through condensers 460 and 461 to the called line. Upon the response of the called subscriber relay 445 energizes, opening the circuit of slow releasing relay 440, which, during its releasing period closes a circuit for tripping machine ringing at the incoming selector. This period is not of sufficient duration to cause the call to be charged on the calling subscribers message register. Since the condensers 460 and 461 are interposed in the estab lished connection, there is no circuit for relay 359 at the incoming selector over the called line, and consequently no charge is made for the call. Talking current is supplied to the called line through the windings of relay 445. If brush selection is made in a group below the one segregated, the wiper 456 engages a segment of the commutator 465, which is isolated from the commutator 455 by the aforementioned saw kerf, and relay 428 does not become energized while sequence switch 400 is in position 2. The final selector then functions in the usual manner.

The final selector switch of Fig. 5 is substantially the same as the switch shown in Fig. 4, but is modified to enable a small group of free lines to be segregated. To accomplish this, the usual tens selection commutator 537 is provided with lugs QX- tending to the edge of the commutator mounting, which may be severed by a saw kerf to divide the commutator 537 into an upper and lower portion. Thus, if it is desired to segregate the free lines in the upper group of ten terminals in the fifth or upper brush group, the commutator 565 is severed at 567 and the commutator 537 is severed at 581. Relay 580 functions in the same manner as relay 128 (Fig. 1) during brush selection, and if tens selection is in the upper tens group, relay 583 energizes and inserts condensers 560 and 561 in the tip and ring conductors of the selector circuit. Machine ringing is then tripped through the action of relays 54 0 and 5 15 in the same manner as in the switch of Fig. 1.

If the selection is in any of the groups below the upper tens group, relay 533 docs not operate and the final selector circuit then functions in the usual manner. If one of the lower brush groups is selected, relay 580 does not function, and consequently if the upper tens group is selected relay 583 does not operate and the selector then functions as usual.

Detail description of operation.

It is thought that a clearer understanding of the invention may be had from a description of the method of establishing a connection. It will first be assumed that the calling subscriber at the substation K desires a connection with a subscriber in his own otfice, whose directory number is PENnsylvania 8432 and whose substation L (Fig. 4), is a free station. The manipulation of the dial to call a free station is the same as for a charge station. Both are made in accordance with ordinary directory numbers. The code or ofiice designation digits set the code registers of the sender mechanism. The code registers govern the setting of a translator to translate the oftice designation digits into district brush and group selection to associate the incoming line and district with a trunk connected to an incoming selector of the proper office. The numerical digits, thousands, hundreds, tens and units set corresponding registers in the sender mechanism which translate the digits into automatic switch control. The thousands register controls incoming brush selection and thus controls the selection of a major group of final selectors. A. combination of the thousands and hundreds registers controls incoming group selection of a minor group within the major group. The incoming selector automatically hunts for an idle trunk in the minor group. This trunk is connected to a final selector. The hundreds register controls the choice of the final selector brush and thus controls the selection of a particular major group of lines. The tens register controls the selection of a particular group of ten lines and the units register controls the selection of a particular line of the desired number in the group of ten. Reference is made to the previously mentioned patent to F. A. Stearn and F. J. Scudder for a more detailed description of the relation between the interruptions transmitted from the dial and the control of the automatic selector switches. The calling subscriber upon removing his receiver to initiate the call, establishes a circuit for the line relay 101 which closes a circuit for the stepping magnet 105 of the line switch 100. The line switch is then rotated by the magnet 105 in search of an idle district selector link terminating in its bank contacts. When an idle district link is found, cut-off relay 102 energizes in the circuit extending through the winding of message register magnet 119 and the winding of sleeve relay 226. Magnet 119, being marginally wound, does not receive sufficient current to operate at this time, but cut-elf relay 102 operates, arresting the hunting movement of the line switch and cutting the line conductors 103 and 104 through to the conductors 116 and 117 of the selected district link over wipers 11.2 and 113 of the line switch 100. Sleeve relay 226 upon operating functions to advance the district selector sequence switch 200 out of position 1 into position 2, in which position the sender finder switch SF (Fig. 1) functions in the well known manner to hunt for and connect with an idle register sender. As soon as an idle register sender is found, relay 235 energizes and sequence switch 200 advances out of position 2 into position 3.

TVith sequence switch 200 in position 3 the calling subscribers line is connected over conductors 116 and 117, contacts of cams 212 and 213, conductors 2 10 and 241, armature contact of relay 235, brushes 150 and 151 of the sender finder switch SF with the pulsing relay 1.52 of the selected sender. The calling subscriber now receives the usual dialing tone and proceeds to dial the number of the desired line, setting the registers of the sender to record the number. As soon as the code letters PEN of the subscribers number have been recorded, the sender functions to set the district selector brushes upon the terminals of an idle trunk outgoing to the office in which the desired line terminates. The fundamental circuit over which brush and group selection movements of the district selector are controlled in positions 4 and 6, respectively, of sequence switch 200 may be traced through the left winding and left armature of control relay 228, relay 228 having energized in the well known manner in position 3 of sequence switch 200, the left contacts of cam 210., the inner right armature of relay 235, brush. 153 of switch SF, windings of sender stepping relay 154E, armature and back contact of counting relay 155, lower left and upper right contacts of cam 157, to ground. Under the control of the sender and the switch control relay 228, the district selector is set and an idle trunk selected in the man ner fully described in the aforesaid patent. Following the selection of an idle trunk, which will be assumed to be the trunk 319, 320 terminating in the incoming selector switch 350, the sequence switch 200 of the district selector advances into position 10, extending a fundamental circuit from the sender over the lower contacts of cams 218 and 219, brushes 263 and 264 of the district selector 250 and trunk conductors 319 and 320, to the control relay 321 of the incoming selector 350. Under the control of the sender in accordance with the first two numerical digits of the desired line number, the incoming selector is selectively operated to extend a connection to an idle final selector switch having access to the desired line. The selective movements of the incoming selector are controlled by relay 321 with sequence switch 300 in positions 2, and 0. It will be assumed that the incoming selector selects the trunk 41?, 419 extending to the final selector switch 450 of Fig. 4. The manner in which the incoming selector switch is operated will not be described herein since the operation thereof enters only incidentally into the disclosure of the present invention. For a detailed description of the operation of this switch, reference may be had to the previously mentioned patent to F. A. Stearn and F. J. Scudder.

Upon the deenergization of control relay 321 following the centering of the brushes 346, 348 and 342 of the selector switch 350 upon the terminals 347, 349, 3.31 of the selected trunk 417, 419, sequence switch 300 advances into position 7, in which position relay 321 again energizes in a circuit extending through its left winding and the right contacts of cam 311 and closes a circuit for advancing sequence switch 300 out of position 7 into position 8, in which position the tip conductor of the fundamental circuit is extended through the resistance element 324, the upper left contact of cam 313, brush and bank terminal 347, trunk conductor 417, the lower left contact of cam 402 (15 to 6), the lower left contact of cam 403 (1), the right winding of relay 418, and thence to battery through the upper left contact of cam 404 (1 to 10). The ring conductor of the fundamental circuit extends as previously traced over conductor 320, the lower contact of cam 304, resistance 325, thence to ground at the lower contact of cam 305 (1 to 8). Upon the extension of the connection to the final selector switch, relay 321, which was energized in position 7 by sequence switch 300, is maintained energized in position 8 of sequence switch through the right winding of relay 321, conductor 322, the right contacts of cam 302, conductor 328, the right armature and front contact of relay 321, conductor 329, the lower right contact of cam 314 (7 to 8), brush 348, terminal 349, trunk conductor 41.9, the upper left and lower right contacts of cam 405, resistance element 420, and thence to ground through the lower left contact of cam 406 (1 to 8 Busy ground potential is placed on the multiples of test terminal 351 of the selected trunk over test brush 342 and the lower right and upper left contacts of cam 312.

Upon the extension of the fundamental circuit to the final selector switch 450, relay 418 of the final selector and stepping relay 154 of the office sender energize. Relay 418 upon energizing closes a circuit for relay 421 which may be traced from battery through the left winding of this relay, conductor 422, the upper left contact of cam 407' (1), conductor 423, the left armature and front contact of relay 418, and thence to ground through the upper contact of earn 408 (1 to 11). Relay 421 energizes and at its left armature and front contact closes a locking circuit for itself from grounded battery through its left winding, the armature and back contact of test relay 424, the left armature and front contact of relay 421, sleeve conductor 425 of the trunk circuit extending back to the incoming selectorswitch thence to ground over bank terminal 351. Relay 421 upon energizing also closes a circuit for driving sequence switch 400 out of its normal position into position 2, which circuit may be traced from battery, through the winding of magnet. of sequence switch 400, the lower contacts of cam 409, and to ground at the right armature and front contact of relay 421. )Vhen sequence switch 400 moves out of position 1, the initial energizing circuit of relay 418 is opened at the lower left contact of cam 403, but relay 418 remains energized over the fundamental circuit by means of a locking circuit extending from battery, through the left contact of cam 404, the right winding of relay 418, the lower right contact of cam 410 (15 to 10), the right armature and front contact of relay 418, the lower right contact of cam 403 (1 to 6), and over the fundamental circuit as previously traced.

Relay 418 when energized with sequence switch 400 in position 2, closes a circuit for the high speed updrive magnet 426, which may be traced from battery, through the upper right contact of cam 411 (2), conductor 423, the left armature and front contact of relay 418, and thence to ground at the upper left contact of cam 408. Magnet 426 upon energizing causes the switch shaft carrying the usual five sets of brushes to move 300 over a circuit extending from battery, upwardly at a high speed in its brush selection movement. As the brush shaft ap proaches its first brush tripping position, wiper 432 engages the lowermost metallic segment of the commutator 430 and a circuit is closed in shunt of the windings of the sender stepping relay 154, which may be traced from battery, through the left contact of cam 404, the right winding of relay 418, the lower right contact of cam 410, the right armature and front contact of relay 418, the lower right contact of cam 403, the upper right contact of cam 402, conductor 429, commutator 430, wiper 432, conductor 433, and thence to ground through the upper left contact of cam 406. Upon the establishment of this shunt circuit, relay 418 at the final selector switch is maintained energized, but stepping relay 154 of the office sender deenergizes.

As the switch shaft continues in its upward movement, the shaft wiper 432 advances into engagement with an insulating segment of the commutator 430, and the shunt circuit previously traced is opened, whereupon the sender stepping relay 154 again energizes. In this manner, as the switch continues in its upward movement, stepping relay 154 of the sender is intermittently operated, until, in the well known manner, the counting relays of the sender have been energized in pairs in accordance with the hundreds digit 4 of the desired line number, when the counting relay 155 energizes and opens the fundamental circuit.

During the brush selection movement of the switch the shaft wiper 456 has advanced over the segments of the lower portion 465 of commutator 455, but since in the case assumed only the upper brush group is reserved for free lines, the first four segments of this portion 465 are isolated and the shaft wiper 456 is without function while passing thereover. lVhen, however, the shaft wiper 456 engages the fifth segment of the commutator portion 465, with the sequence switch 400 in position 2, a circuit is established for relay 428 which may be traced from battery, through the winding of this relay, the contact of cam 466,the fifth segment of commutator 465, shaft wiper 456 and to ground at the upper left contact of cam 406. Relay 428 thereupon energizes and looks over its inner left armature and contact to ground at the upper left contact of cam 414, this locking circuit being maintained until the sequence switch 400 leaves position 18 following the restoration of the final selector. Relay 428 at its outer left contact prepares a circuit for relay 445 and at its right armatures and front contacts connects the tip and ring conductors of the final selector trunk to the winding and armature contact, respectively, of relay 440. Relay 428 also at its right armatures and back contacts opens the direct metallic conof position 3 and into position 4.

nection between the tip and ring conductors of the selected trunk circuit and the brushes 452 and 453 of the switch and interposes the condensers 460 and 461 therebetween.

If the hundreds digit dialed had been such as to have arrested the brush selection movement of the selector switch before reaching the fifth segment in the commutator 465 for extending a connection to a line terminating in any of the first four brush groups of the switch, then the relay 428 would not have become energized as previously described and consequently relays 440 and 445 would not enter into the opera tion of the selector switch and the selector switch would therefore function from that point in the manner fully set forth in the aforesaid patent.

As soon following the opening of the fundamental circuit as the wiper 432 engages the next insulating segment of the commutator 430, relay 418 becomes deenergized and at its left armature and front contact opens the operating circuit of the updrive magnet 426 to arrest the upward move ment of the switch shaft. At its left armature and back contact relay 418 closes a circuit for advancing sequence switch 400 out of position 2 into position 3, this circuit extending from battery, through the winding of sequence switch magnet 400, the upper right contact of cam 412 2), the left armature and back contact of relay 418, and thence to ground at the upper contact of cam 408. The fifth set of brushes has now been positioned with relation to the tripping fingers of the trip spindle (not shown) so that upon a subsequent upward movement of the switch shaft, this set of brushes will be tripped for engagement with the bank of 100 terminals with which this brush set is associated. To cause the tripping of this set of brushes the tripping magnet 435 is energized as soon as sequence switch 400 reaches position 3 over a circuit extending from battery, through the magnet 435, and thence to ground through the lower right contact of cam 406 (3 to l/Vhen sequence switch 400 reaches position 3 the energizing circuit of relay 418 is again established over the fundamental circuit as previously described and relay 418 and stepping relay 154 of the sender again energize. Relay 418 upon energizing closes th previously traced circuit for driving sequence switch 400 out lVith sequence switch 400 in position 4, the circuit for the updrive magnet 426 is again established at the left armature and front contact of relay 418. Relay 418 also establishes the previously traced locking circuit for itself extending through its right armature and front contact for maintaining itself energized over the fundamental cireuit, after sequence switch 400 leaves position 3.

Upon the energization of the updrive magnet 426, the switch shaft is driven upwardly in its group selection movement, during the initial operation of which the fifth set of brushes is tripped. During the remainder of the group selection movement the tripped set of brushes, which will be assumed to be the brushes 452, 453, 442, then travel upwardly in contact with the terminals of the bank with which they are associated. As the brushes approach the first set of terminals of the first group in the bank, shaft wiper 438 engages a metallic portion of the group selection commutator 437 and a circuit is closed in shunt of the windings of stepping relay 154 which may be traced from battery, through the left contact of cam 404 (1 to 10), the right winding of relay 418, the lower right contact of cam 410, th right armature and front contact of relay 418, the right contacts of cam 403, conductor 436, commutator 437, wiper 438, conductor 433, and thence to ground at the upper left contactof cam 406. Relay 418 at the final selector switch is maintained energized over this shunt circuit, but the sender stepping relay 154 becomes deenergized so long as the shunt circuit is maintained.

As the switch shaft continues in its up ward movement the wiper 438 engages an. insulating portion of the. commutator 437, and the previously traced shunt circuit is opened and stepping relay 154 of the sender again energizes. In this manner as the switch shaft continues its upward movement the sender stepping relay 154 is intermittently operated until the counting relays have been operated in pairs in accordance with the registration of the tens digit of the desired number, when the counting relay 155 energizes, opening th fundamental circnit.

As soon following the opening of the fundantiental circuit as wiper 438 engages the next insulating portion of commutator 4237, relay 418 becomes deenergized and opens the circuit previously traced through the winding of the updrive magnet 426 and closes the circuit previously traced for advancing sequence switch 400 out of position 4 into position 5. In position 5 the fundamental circuit extending through the windings of sender stepping relay 154 and the right winding of relay 418 is again established. Relay 418 upon energizing closes the previously traced locking circuit for itself and closes a circuit for driving sequence switch 400 out of position 5 and into position 6. Upon reaching position 6 a circuit is established for low speed updrive magnet 439, which circuit may be traced from battery, through the winding of magnet 439, the lower left contact of cam 407, conductor 423, the left armature and front contact of relay 418, and thence to ground at the upper left contact of cam 408. The low speed updrive magnet 439 upon energizing advances the switch shaft in its units selection movement.

As the tripped set of brushes approaches the first set of terminals in the selected group the shaft wiper 432 engages a metallic segment of the units selection portion of commutator 430, and a circuit is closed in shunt of the sender stepping relay 154, which may be traced from battery, through the left contacts of cam 404, the right winding of relay 418, the lower right contact of cam 410, the right armature and front contact of relay 418, the lower right contact of cam 403, the upper right contact of cam 403, conductor 429, commutator 430, wiper 432, conductor 433, and thence to ground at the upper left contact of cam 406. Relay 418 is maintained energized over this shunt circuit but stepping relay 154 deenergizes. As the switch shaft continues its upward movement wiper 432 comes into engagement with an insulating segment of commutator 430, and the previously traced shunt circuit is opened, whereupon the sender stepping relay 154 again energizes. In this manner during the continued upward movement of the switch shaft the sender stepping relay 154 intermittently energizes and deenergizes until the counting relays of the sender have been energized in pairs in accordance with the setting of the units register of the sender, when relay 155 energizes, opening the fundamental circuit.

As soon following the opening of the fun damcntal circuit as the wiper 432 engages the next insulating segment of commutator 430, relay 418 becomes deenergized and opens the circuit of the updrive magnet 439 to arrest the upward movement of the switch shaft and closes the previously traced circuit for driving sequence switch 400 out of position 6 and into position 9. The brushes of the final selector switch 450 have now been positioned upon the bank terminals, which are numbered 8432. lVith the sequence switch 400 in position 9 a circuit is now closed for reenergizing relay 418, which may be traced from battery, through the left contact of cam 404, the right winding of relay 418. the lower right and upper left contacts of cam 410. and thence to ground at the right armature and front contact of relay 421. Relay 418 upon energizing closes a locking circuit for itself extending from battery, through its right winding, the lower right contact of cam 410, the right armature and front contact of relay 418, and thence to ground through the upper contacts of cam 413. This locking circuit will be maintained through position TELEPtiQNY.

10 of switch 400. Relay 418 upon energizing also closes a circuit as previously traced for driving sequence switch 400 out of posi tion 9, the switch continuing to advance under the influence of master cam 401, through intermediate positions into position 12. Upon reaching position 10 a new holding circuit is established for relay 418 extending from battery, through the left winding of relay 418, the lower right contact of cam 415, the left armature and front contact of relay 418, and thence to ground at the upper left contact of cam 408. Upon reaching position 11 sequence switch 400 establishes a new circuit for relay 418 eXtend ing from ground, through the winding of test relay 424, conductor 441, the upper left contact of cam 402, the lower left contact of cam 403, the right winding of relay 418 and the upper right contact of cam 410, the right armature and front contact of relay 418, the right contacts of cam 413, test brush 442, and thence to ground on the test terminal 464, it being assumed that the desired lin L is idle. When the test brush 442 encounters test terminal 464 the circuit previously traced through the winding of relay 418 and the winding of test relay 424 will extend from ground to ground and relay 418 will thereupon deenergize, opening the circuit of the updrive magnet 439 and clos ing a circuit for driving sequence switch 400 out of position 12 and into position 13. This circuit extends from battery, through the upper right contact of cam 412, the left armature and back contact of relay 418, the lower left contact of cam 408, and thence to ground at the right armature and front contact of relay 421.

To insure that relay 418 will not be de energized upon brush 442 reaching the terminal of the selected line to stop the upward movement of the switch shaft before the brushes have been properly set on the terminals of the selected line, relay 418 is locked over a circuit extending from battery, through the left winding of relay 418, the lower left contact of cam 415 (12), the right winding of relay 421, conductor 454, centering commutator 455, wiper 456, conductor 433, the upper right contact of cam 407 (12), conductor 423, the left armature and front contact of relay 418, the lower left contact of cam 408, and thence to ground at the right armature and front contact of relay 421 this circuit being maintained until wiper 456 engages an insulating segment of commutator 455 corresponding to the centered position of the brush set upon the terminals of the selected line.

Upon reaching position 13 a circuit is established over the lower contacts of cam 409 and the right armature and front contact of relay 421 for driving sequence switch 400 out of position 13 into position 14, and

in position 14 a circuit is established as previously traced through the magnet winding of sequence switch 400, the upper right contact of cam 412, the left armature and back contact of relay 418, and thence to ground at the upper left contact of cam 408 for driving the sequence switch into the talking position 15. The trunk conductor 417 is now connected over the lower contacts of cam 402, the outer right armature and front contact of relay 428, condenser 461, to brush 452, and trunk conductor 419 is similarly connected over the upper con tacts of cam 405, the inner right armature and front contact of relay 428, condenser 460, to the switch brush 453.

Following the units selection movement of the final selector switch and the advance of sequence switch 400 from position 6 into position 9, the circuit previously traced over the lower right contact of cam 405 (1 to 8 and through the winding of relay 321 of the incoming selector is opened, and relay 321 deenergizes. Relay 321 upon deenergizing closes a circuit for advancing sequence switch 300 out of position 8 into position 9, which circuit may be traced from battery, through the winding of the magnet of sequence switch 300, the upper left contact of cam 306, and thence to ground at the iiiner left armature and back contact of relay 321. \Vith sequence switch 300 in position 9 relay 321 is again connected to the fundamental circuit extending back to the sender in such a manner that the circuits function i in the manner described in the aforesaid patent for causing the advance of the sequence switch 200 of the district selector out of the selection beyond position 10 into a talking selection posit-ion. Talking selection thereupon is effected, it being assumed that on a call of the character described the sequence switch 200 of the district selector is arrested in position 12. As soon as sequence switch 200 leaves position 10 the impulse leads 240 and 241 are disconnected and the sender is restored to its normal condition. The trunk conductors 116 and 117 are thereupon connected over contacts of cams 212 and 213 through the winding of supervisory relay 269 and the left windings of repeating coil 267. and the polarized relay 268 is connected through the right windings of repeating coil 267 and over contacts of cams 218 and 219 to the brushes 263 and 264 of the district selector.

During the setting of the sequence switch 200 of the district selector into its talking position, sequence switch 300 of the incoming selector switcn 300 has been standing in position 9. In position 9, with relay 321 energized over the fundamental circuit, a circuit for energizing relay 371 is established from battery, through the winding of relay 371., the right contact of cam 316 (9 to 10), the right armature and front contact of relay 321, conductor 329, and thence to ground through the upper contacts of cam 312. Relay 371 upon energizing closes a circuit for advancing sequence switch 300 out of position 9 extending from battery, through the sequence switch magnet, armature and front contact of relay 371, and thence to ground through the left contacts of cam 312. Upon leavng position 9, the fundamental circuit attending to the sender is opened and relay 321 deenergizcs, opening the circuit of relay 371 to arrest sequence switch 300 in position 10.

A, soon as sequence switch 300 moves into position 10, if at the time sequence switch 200 of the district selector has advanced to the selected talking position, a circuit is established for relay 321 extending through the right winding of this relay, the upper contacts of cam 302, conductor resistance element 324, upper contact of cam 303, trunk conductor 319, bank terminal 260 and brush 263 of the district selector, the upper contacts of cam 218, the uppermost right winding of repeating coil 267, the upper contacts of cam 220, the windings of polarized relay 268, the lower contact of cam 221, the lowermost right winding of repeating coil 267, the upper contacts of cam 219, brush 264, and terminal 259 of district selector switch 250, trunk conductor 320, the lower contact of earn 304, resistance element conductors 326, and thence through the lower contact of cam 305, to ground. Relay 321 upon energizing locks to ground through the lower contact of cam 307 over a circuit extending from battery through its left winding. the armature and back contact of relay 355, the upper left contact of cam 309, the outer left armature and front contact of relay 321, conductor 327, and thence to ground at cam 307. W hen sequence switch 300 leaves position 10, locking ground is supplied over conductor 364 and the upper contact of cam 307, test terminals 258, brush 257, to ground at the right contacts of cam 215. When relay 321 reenergizes, the circuit of relay 371 is again established and. the sequence switch 300 driven out of position 10 into position 11. With sequence switch 300 in position 11 the circuit of relay 371 is again established over the upper contact of cam spring 352 of the interrupter and the upper left contact of cam 316 (11). A circuit is also established in position 11 extending from ground at the right contact of cam 313, brush 346 and terminal 347 of switch 350, trunk conductor 417, the lower contacts of cam 402, the outer right armature and front contact of relay 428, winding of relay 440, armature and back contact of relay 445 to battery, and relay 440 energizes. A circuit is also established for supplying a steady flow of ringing current to the called line which may be traced from the source of ringing current 354, through the lower left and upper right contacts of cam 317, the winding of ringing trip relay 355, the lower contacts of cam 302, conductor 328, the right armature and front contact of relay 321. conductor 329, the lower right contact of cam 314, brush 348 and terminal 349 of switch 350, trunk conductor 419, the upper contacts of cam 405, the inner right armature and front contact of relay ,428, condenser 460, brush 453, terminal 463, through the call bell of the line 1 and returning over terminal 462, brush 4.52, condenser 461, the outer right armature and front contact of relay 428, the lower contacts of cam 402, conductor 417, bank terminal and brush 346 of switch 350, to ground at the right contact of cam 313.

soon as relay 371 energizes in position 11 of sequence switch 300, the circuit previously traced through the armature and front contact of relay 371 is again established for driving sequence switch 300 out of position 11. Upon leaving position 11 the circuit of relay 371 is opened and the sequence switch is arrested at position 12. In position 12 relay 371 is again energized as soon as a circuit therefor is established over the lower left contact of cam 316 (12), and the lower contact of spring 352 of the interrupter 353, and upon its energization drives sequence switch 300 out of position 12 into position 13. In position 13 the source of ringing current 354 is connected over the circuit previously traced through the interrupter 356 and the right contacts of cam 317, and this circuit is maintained until the ringing current is tripped.

When the called subscriber removes his receiver in response to the ringing of his call bell, a circuit is established over his line loop for relay 445 which may be traced from battery, through the left winding of this relay, the outer left armature and contact of relay 428, brush 453, bank terminal 463, over the subscribers line loop returning through bank terminal 462, brush 452, to ground through the rightwinding of relay 445. Relay 445 thereupon energizes, opening at its armature and back contact the previously traced circuit for relay 440. Relay 445 at its armature and front contact now establishes a circuit which is effective during the releasing period of the slow releasing relay 440 for tripping ringing current at the incoming selector switch. This circuit may be traced from battery, through the armature and front contact of relay 445, resistance 427, the armature and front contact of relay 440, the inner right armatureand front contact of relay 428, the upper contacts of cam 405, trunk conductor 419, thence as previously traced through the winding of marginal relay 355 to the ringing generator 354. The current now flowing through the winding of relay 355 is of sufficent strength to cause its energization. Relay 355 upon energizing opens at its armature and back contact the locking circuit obviously traced through the left winding of relay 321, and relay 321 thereupon deenergizes, opening the circuit previously traced over which ringing current was transmitted to the called line, and closing a circuit through its inner left armature and back contact extending through the upper left contact of cam 306 for driving sequence switch 300 out of position 13 and into the talking position 16. lVhen sequence switch 300 passes through position 14 relay 321 again energizes over a circuit extending from battery, through its left winding and the right contacts of cam 311 and closes a locking circuit for itself extending through its left winding, the armature and back contact of trip relay 355, relay 355 having deenergized when sequence switch 300 left position 13, the upper left contact of cam 309, conductor 331, the outer left armature and front contact of relay 321, conductor 327, the upper contact of cam 307, and thence over sleeve conductor 36 4, to ground through the contact of cam 215 at the district selector switch. It is to be noted that the circuit through the tripping relay 355 at the incoming selector switch was effective only during the releasing period of the slow releasing relay 440, and was therefore opened before sequence switch 300 reached position 14 and connected relay 359 to the trunk conductors 417 and 419. As soon as sequence switch 300 reaches position 14 a talking path is established through the lower right winding of repeating coil 358, the winding of relay 359, the upper contact of cam 314, brush 348 and bank terminal 349, trunk conductor 419, the upper contacts of cam 405, the inner right armature and front contact of relay 428, condenser 460, brush 453 and bank terminal 463 of the final selector switch, thence over the called line, returning over terminal 462 and brush 452, condenser 461, the outer right armature and front contact of relay 428, the lower contacts of cam 402, trunk conductor 417, bank terminal 347 and brush 346 of switch 350, the lower contact of cam 313, and thence to ground through the upper right winding of repeating coil 358. Since condensers 460 and 461 are included in this circuit, relay 359 does not energize. With relay 359 deenergized no reversal of current through the winding of polarized relay 268 is made at this time, and consequently the usual charging condition established through the operation of relay 261 for charging the call on the calling subscribers message register 119 is not made. The talking circuit between the calling subscribers station K and the called subscribers station L extends over the conductors shown in heavy lines in the drawings, the calling subscriber being supplied with talking current through the left windings of repeating coil 267 at the district selector 250 and the called subscriber being supplied with talking current through the windings of relay 445. Upon the termination of the conversation the swiches are restored in the well known manner as fully set forth in the aforementioned patent, relay 428 becoming unlocked when the sequence switch 400 of the final selector passes out of position 18 and relay 445 becoming deenergized when the called subscriber restores his receiver to its switchhook.

If the calling subscriber had desired a connection with a subscribers line terminating in one of the first four brush groups of the final selector switch and had dialed a number, for example, 8132 instead of 8432, then the second set of brushes of the final selector switch would have been selected and relay 428 would not have been energized when sequence switch 400 was in position 2, as previously described. Consequently when the sequence switch 400 of the final selector switch reaches the talking position 15, the tip and ring conductors 417 and 419 are connected over the contacts of cams 402 and 405 through the right armatures and back contacts of relay .428 to the tip and ring brushes 452 and 453 of the switch, and ringing current passes over a full metallic circuit to the called line. Therefore when the called subscriber answers, ringing trip relay 355 is energized over the called line loop and following the tripping of ringing current the supervisory relay 359 becomes energized over the called line. With relay 359 energized current is reversed through the windings of polarized relay 268 at the district selector, and in the manner set forth in the aforesaid patent charging relay 261 of the district is energized and looked through the contacts of cam 205. WVhen, therefore, the calling subscriber restores his receiver to the switchhook following the termination of the conversation and the sequence switch 200 of the district selector advances into position 17, a circuit is established for increasing the strength of current flowing through the winding of cut-off relay 102 and the winding of the message register magnet 119, this circuit now extending from ground through the winding of relay 102, the intermediate lower armature of relay 102, winding of message register magnet 119, wiper 109, conductor 118, left contact of cam 203, left armature and front contact of relay 261, left non-inductive winding of relay 226, outer left armature and front contact of relay 226. to battery through the upper contacts of are cam 224. The message register magnet 119 now operates and the successful call is charged in the usual manner.

If the number of free lines exceeds 100 or the number of lines accessible in one brush group of the final selector, and, for example, consists of approximately 200 lines, then the commutator l would be severed from the comn'iutator L55 at the point 468 rather than at the point 467 so that when the shaft wiper 4.56 reaches the fourth metallic segment of commutator 4:65, relay 428 becomes energized, and consequently if the brushes of the switch. are arrested in a position to trip either the fourth or fifth set of brushes the circuits of the final selector are so modified as to prevent charging the call against the calling subscriber.

Number of free Zines less than brush group.

In the preceding description it has been assumed that the number of free lines in the exchange office to be served is substantially a full brush group or more than a brush group, that is, with the type of switch under consideration, approximately 100 lines or more than 100 lines. The number of free lines, however, is usually less than 100, and therefore it would not be entirely economical to reserve a complete brush group of 100 lines for such service since a great number of the terminals of the final selector switches will in that case be left blank and the elliciency of the switch will be to that extent decreased. The modification of the invention disclosed in Fig. 5 is designed to permit the more economical use of the finalv selector switches by allowing the segregation of free lines in only a portion of a brush group, thereby permitting the remaining portion of such brush group and the other brush groups of the switch to be used in regular service. It will therefore be assumed that it is only necessary to reserve a tens group of ten lines for free line service and that this tens group is the uppermost in the fifth brush group.

Upon the seizure of the finalv selector switch 550 by the incoming selector 350 the relays 521 and 518 function in the same manner as the corresponding relays of Fig. at and sequence switch 500 is advanced into position 2. With sequence switch 500 in position 2 the circuit of the updrive magnet 526 is established and the brushes of the switch are driven upwardly in the brush selection movement. As the wiper 532 passes over the brush selection segments of commutator 530, the sender counting relays are operated in the well known manner until the sender is satisfied in accordance with the setting of its hundreds register. Also during the brush selection movement of the switch the shaft wiper 556 passes over segments of the commutator 565, but is without effect while passing over the first four segments corresponding to the lower four brush selection positions of the switch since these lower segments are isolated at 567. hen the shaft wiper 556 reaches the fifth segment just above the break 567, a circuit is established for relay 580 which may be traced from battery, through the winding of relay 580, sequence switch cam 566 (1% to 2), commutator 555, shaft wiper 556, thence to ground at the upper left contact of cam 506. Relay 580 upon energizing locks over its left armature and front contact to ground at the upper left contact of cam 51%, this locking ground being maintained until after the switch is restored to normal following the termination of the conversation.

Since it is assumed that the desired line terminates in the fifth brush group, the fundamental circuit is opened after five impulses h ave been transmitted from the switch through shaft wiper 532 and commutator 530. As soon as the fundamental circuit is opened relay 518 deenergizes and causes the movement of sequence switch 500 out of position 2 into position 3. In position 3 the fundamental circuit extending through the right winding of relay 518 and the windings of tender stepping relay 154: is again established in the well known manner and sequence switch 500 is advanced into position 4, in which position relay 518 is locked to the fundamental circuit. With relay 518 energized and sequence switch 500 in position 4 the circuit of the updrive magnet 526 is again established for driving the switch shaft upwardly in its group selection movement. During the initial portion of this movement the fifth set of brushes is tripped because of the operated condition of tripping magnet 535, which magnet operated when sequence switch cam 506 closes its lower right contact in position 3. During the continued movement of the switch shaft, the shaft wiper 538 engages the lowermost conducting portion of commutator 537 as the tripped set of brushes approach their first group selecting position. A circuit is now established in shunt of the windings of sender stepping relay 154, which may be traced from battery, through the left contact of cam 504, the right winding of relay 518. lower right contact of cam 510, the right armature and front contact of relay 518, the right contacts of cam 503, conductor 536. commutator 537, wiper 538, to ground at the upper left contact of cam 506. Relay 518 is maintained; energized over this shunt circuit. The sender stepping relay 15; becomes deenergized so long as the shunt circuit is maintained. As the switch shaft continues in its upward movement wiper 538 engages an insulating por- "iii tion of the commutator 537 and the previ-' ously traced shunt circuit is opened and stepping relay 154 of the sender again energizes. In this manner as the switch shaft continues its upward movement the sender stepping relay 154 intermittently energizes and deenergizes. After the shaft wiper leaves the ninth conducting segment of commutator 537 as the tripped set of brushes is approaching the tenth group of contacts in the fifth brush group, the previously traced shunt circuit extending over conductor 536 and through the winding of relay 518 is without effect and a new shunt circuit is established as soon as the shaft wiper 538 engages the conducting segment immediately preceding the tenth group, this segment being separated from the other nine segments of the commutator through the kerf 581 made in the edge of the commutator mounting. The new shunt circuit may be traced from the right hand armature and front contact of relay 518, the right contacts of cam 503, the right winding of relay 583 the outer right armature and front contact of relay 580, the upper portion of commutator 537 above the kerf 581, shaft wiper 538, and thence to ground at the left contact of cam 506. This circuit shunts the sender stepping relay 154 and causes the energization of relay 583 at the final selector. Relay 583 upon energizing looks from batery through its left winding, inner left armature and front contact, to ground at the left contact of cam 514. At the Fender, it being assumed that the counting relays are all energized in accordance with the setting of the tens register of the sender, relay 155 opens the fundamental circuit, causing the deenergization of relay 518 and the arresting of the final selector switch shaft in a position immediately beneath the tenth tens group of the fifth brush group.

From this point the final selector functions in the manner previously described in connection with the final selector of Fig. 4 up to the point where ringing current is applied from the incoming selector to ring the called subscriber. At this time the sequence switch 500 is resting in position 15,

and with the sequence switch 300 of the incoming selector in the first ringing position 11, a circuit is established from ground at the right contact of cam 313, over brush 346 and terminal 347 of the incoming selector, trunk conductor 517, the lower contacts of cam 502, the outer right armature and front contact of relay 583, winding of relay 540, the armature and back contact of relay 545, to battery. Relay 540 energizes, preparing a circuit for tripping machine ringing as soon as the called subscriber responds and causes the energization of relay 545. Ringing current is applied to the called line as previously described in connection with Figs. 3 and 4, the ringing circuit being traced at the final selector from trunk conductor 517, the lower contacts of cam 502, the outer right armature and front contact of relay 583, condenser 561, brush 552 and terminal 562 of switch 550, thence through the call bell of the called line, returning over bank terminal 563 and brush 553, condenser 560, the inner right armature and front contact of relay 583, the upper contacts of cam 505, thence over conductor 519.

In response to the ringing of his bell the called subscriber takes his receiver from its switchhook, thereby establishing a circuit for relay 545. This circuit may be traced from battery, through the left Winding of relay 545, the outer left armature and contact of relay 583, brush 553, thence as traced over the subscribers line loop, returning over brush 552 to ground through the right winding of relay 545. Relay 545 upon energizing cooperates with slow releasing relay 540 to trip machine ringing in the manner previously described. From this point the circuits function in exactly the same manner as hereinbefore described in connection with Fig. 4.

It will now be assumed that the calling subscriber calls a line terminating in the first tens group of the fifth brush group. The final selector functions as just described up to the point where tens selection is made, the relay 580 operating as before when shaft wiper 556 engaged the fifth segment of commutator 565. Since it is assumed that selection is to be made in the first tens group, the sender becomes satisfied as soon as the shaft wiper 538 passes the first conducting segment of commutator 537 opening the fundamental circuit and arresting the tripped set of brushes beneath the first tens group of terminals in the fifth brush group. Following the tens selection, sequence switch 500 advances from position 4 into position 6. It will be noted that no circuit has been established for relay 583 and cannot be established after sequence switch 500 leaves position 4 since the circuit for relay 583 is opened at the upper right contact of cam 503. Since relay 583 is not energized when sequence switch 500 reaches position 15, when ringing current is supplied to the called line, the ringing current passes by a full metallic connection over the right armatures and back contacts of relay 583 and the calling subscriber upon responding trips the ringing current in the usual manner and causes the energization of relay 359 at the incoming selector to establish the usual call charging condition at the district selector 250.

If the calling subscriber calls a line terminating in one of the lower brush groups of the final selector 550, the wiper 556 will not engage a segment of the commutator 565 which is connected in circuit with relay 580 during the brush selecting movement of the switch, and consequently if the final selector is later advanced to select a line in the upper or tenth tens group of the selected brush group, no circuit will be established for relay 583 and the final selector will function in the usual manner. The shunt circuit established for shunting the sender stepping relay during tens selection after shaft wiper 53S leaves the ninth conducting segment of commutator 537 may be traced through the right contacts of cam 503, the inner right armature and back contact of relay 580, the upper segment of commutator 537, through shaft wiper 538 to ground at the upper left contact of cam 506. It will thus be noted that with relay 5S0 deenergized, the two portions of the tens selection commutator 537, which are separated by the break 581, are connected together at the inner right armature and back contact of relay 580 so that the commutator 537 function as a whole, and therefore tens selection is made as though the discriminating equipment of the final selector were not present.

lVhile the number of free lines has been disclosed in Fig. 5 as limited to a single tens group, it is obvious that as many tens groups in a brush group may be reserved as desired by breaking the commutator 537 at any of the lugs extending therefrom.

lVhile the invention has been disclosed in connection with a final selector switch of the panel type, it is obvious that it is applicable to any switch of the multibrush type. Further the invention might be employed in a system having any type of call charging device, such as a coin-box.

In the foregoing description it has been pointed out that the commutator of the final selector may be modified for the purposes of this invention by separating segments of the commutator from the commutator 505 and by separating the upper and lower portions of commutator 537 through saw kerfs made in the edges of the commutator mounting. This same result may be accomplished in the manner shown in Fig. 6 by having the segments of the commutator normally separated from each other and from the commutator 555 and by having the segments of commutator 537 normally separated from each other. When it is de sired to join these sections screws may be inserted as shown at 567 and 581. Thus, if a screw is inserted at 567 the upper segment of commutator 565 is joined to the commutator 555 and the upper brush group becomes segregated for free line service. Also, if screws are inserted as at 581 in the openings separating the lower nine segments of commutator 537, only the upper tens group of lines is segregated for free nne service.

Instead of using screws as shown in Fig. (3, the isolated sections of the commutators could be joined by drops of solder. In this manner the commutator may be changed at will to segregate a desired brush group or tens group of a brush group for free line service.

hat is claimed is:

1. In an automatic telephone system, telephone lines, call charging devices individual to said lines, an automatic switch for interconnecting said lines, a plurality of brush sets for said switch, each brush set having access to the terminals of a group of said lines, means for selecting any one of said brush sets, means operative upon the response of a called subscriber for preparing the calling charging device of the calling line for operation, and means actuated only when a certain brush set of said switch is selected for renderin said call charging operating means inoperative.

2. In an automatic telephone system, telephone lines, call charging devices individual to said lines, an automatic switch for interconnecting said lines, a plurality of brush sets for said switch, each brush set having access to the terminals of a group of said lines, means for selecting any one of said brush sets, means operative upon the response of a called subscriber in certain of said groups of lines for preparing the call charging device of the calling line for operation, and means actuated in the selection of a certain brush set for rendering said call charging operating means inoperative upon the response of a called subscriber in the group of lines to which said certain brush set has access.

3. In an automatic telephone system, telephone lines, call charging devices individual to said lines, an automatic switch for interconnecting said lines, a plurality of brush sets for said switch, each brush set having access to the terminals of a group of said lines, means for selecting any one of said brush sets, means operative upon the response of called subscribers in certain of said groups of lines for preparing the call charging device of the calling line for operation, and a relay actuated in the selection of a certain brush set for rendering said call charging operating means inoperative upon the response of a called subscriber in the group of lines to which said certain brush set has access.

4. In an automatic telephone system, telephone lines, call charging devices individual to said lines, an automatic switch for interconnecting said lines, a plurality of brush sets for said switch, each brush set having access to the terminals of a group of said lines, means for selecting any one of said brush sets, means operative upon the response of called subscribers in certain of said groups of lines for preparing the call charging device of the calling line for operation, and means actuated in the selection of certain brush sets for rendering said call charging operating means inoperative upon the response of a called subscriber in the groups of lines to which said certain brush sets have access.

5. In an automatic telephone system, telephone lines, call charging devices individual to said lines, an automatic switch for interconnecting said lines, a plurality of brush sets for said switch, each brush set having access to the terminals of a group of said lines, means for selecting any one of said brush sets, means for extending a full metallic circuit over certain of said brush sets upon connection with lines of groups accessible therefrom, means operative over said circuit upon the response of called subscribers of such groups for preparing the call charging device of the calling line for operation, and means actuated in the selection of a certain brush set for interpolating an inductive link in said circuit for rendering said call charging operating means inoperative upon the response of a called subscriber in the group of lines to which said certain brush set has access.

6. In an automatic telephone system, telephone lines, call charging devices individual to said lines, an automatic switch for interconnecting said lines, a plurality of brush sets for said switch, each brush set having access to the terminals of a group of said lines, means for selecting any one of said brush sets, means for extending a full metallic circuit over certain of said brush sets upon connection with lines of groups accessible therefrom, means operative over said circuit upon the response of called subscribers of such groups for preparing the call charging device of the calling line for operation, and means actuated in the selection of a certain brush set for interpolating condensers in said circuit for rendering said call charging operating means inoperative upon the response of a called subscriber in the group of lines to which said certain brush set has access.

7. In an automatic telephone system, tele phone lines, call charging devices individual to said lines, an automatic switch for interconnecting said lines, a plurality of brush sets for said switch, each brush set having access to the terminals of a group of said lines, means for selecting any one of said brush sets, means for extending a full metallic circuit over certain of said brush sets upon connection with lines of groups accessible therefrom, means operative over said circuit upon the response of called subscribers of such groups for preparing the call charging device of the calling line for operation, and a relay actuated in the selection of a certain brush set for interpolating condensers in said circuit for rendering said call charging operating means inoperative upon the response of a called subscriber in the group of lines to which said certain brush set has access.

8. In an automatic telephone system, telephone lines, call charging devices individual to said lines, an automatic switch operable in a plurality of selective movements for interconnecting said lines, means operative upon the response of called subscribers for preparing the call charging device of the calling line for operation, and means actuated in response to a plurality of said selective movements of said switch for rendering said call charging operating means inoperatlve.

9. In an automatic telephone system, telephone lines, call charging devices individual to said lines, an automatic switch operable in a plurality of selective movements for interconnecting said lines, means operative in certain selective positions of said switch upon response of called subscribers for preparing the call charging device of the call ing line for operation, and means actuated in response to a plurality of said selective movements of said switch to render the response of other called subscribers ineffective to operate said call charging operating means.

10. In an automatic telephone system, telephone lines, call charging devices individual to said lines, an automatic switch operable in a plurality of selective movements for interconnecting said lines, means operative in certain selective positions of said switch upon response of called subscribers for preparing the call charging device of the calling line for operation, and relay means actuated in response to a plurality of said selective movements of said switch to render the response of other called subscribers ineffective to operate said call charging operating means.

11. In an automatic telephone system, telephone lines, call charging devices individual to said lines, an automatic switch operable in a plurality of selective movements for interconnecting said lines, means operative in certain selective positions of said switch upon response of called subscribers for preparing the call charging device of the calling line for operation, a relay actuated if one of said selective movements is extended to a certain point, a second relay actuated if a second of said selective movements is extended to a certain point, and means under the joint control of said relays to render the response of other called subscribers ineffec tive to operate said call charging operating means.

12. In an automatic telephone system, telephone lines, call charging devices individual to said lines, an automatic switch operable in a plurality of selective movements for interconnecting said lines, means operative in certain selective positions oil? said switch upon response of called subscribers for preparing the call charging device of the calling line for operation, a relay actuated if one of said selective movements is extended to a certain point, a second relay actuated it said lirst relay is operated and a second selective movement of said switch is extended to a certain point, and means under the joint control of said relays to render the response of other called subscribers ineitective to operate said call charging operating means,

13. In an automatic telephone system, telephone lines, call charging devices individual to said lines, an automatic switch having a plurality of brush sets for interconnecting said lincs, each of said brush sets having access to a group oi lines, means for selecting any one of said brush sets, means for moving a selected brush set in a plurality of selective movements, means operative in certain selective positions of said switch upon response ofcalled subscribers for pre paring the call charging device of the calling line for operation, and means operated in certain selective positions of one of said brush sets to render the response of other called subscribers ineffective to operate said call charging operating means.

14. In an automatic telephone system, telephone lines, call charging devices inclividual to said lines, an automatic switch having a plurality of brush sets for interconnecting said lines, each brush set having access to the terminals out a group of said lines, means for selecting any one of said brush sets, means operative upon the response of called subscribers in certain of said groups of lines for preparing the call charging device of the calling line for operation, means actuated in the selection of certain brush sets for rendering said call charging operating means inoperative upon the response of a called subscriber in the groups of lines to which said certain brush sets have access, and means for at will varying the number or such certain brush sets.

15. In an automatic telephone system, telephone lines, call charging devices individual to said lines, an automatic switch having a plurality of brush sets for interconnecting said lines, each of said brush sets having access to a group of lines, means for selecting any one of said brush sets, means for moving a selected brush set in a plurality of selective movements, means operative in certain selective positions of said switch upon response of called subscribers for preparing the call charging device of the calling line for operation, means operated in certain selective positions of one of said brush sets to render the response of other called subscribers ineffective to operate said call charging operating means, and means for at will varying the number of said certain selective positions.

16. In an automatic telephone system, telephone lines, call charging devices individual to said lines, an automatic switch operable in a plurality of selective movements for interconnecting said lines, a commutator for said switch for controlling its selective movements, means operative in certain selective positions of said switch upon response of called subscribers for preparing the call charging device of the calling line for operation, means controlled by segments of said commutator in response to a plurality of said selective movements of said switch to render the response of other called subscribers ineffective to operate said call charging operating means, and means for at will altering the effect of said com1nutator on said last named means.

17. In an automatic telephone system, telephone lines, call charging devices indi vidual to said lines, an automatic switch for interconnecting said lines, a plurality of brush sets for said switch, each brush set having access to the terminals of a group of said lines, means for selecting any one of said brush sets, means for extending a full metallic circuit over certain of said brush sets upon connection with lines of groups accessible therefrom, means operative over said circuit upon the response of called subscribers of such groups for preparing the call charging device of the calling line for operation, means actuated in the selection of a certain brush set for interpolating an inductive link in said circuit for rendering said call charging operating means inoperative upon the response of a called subscriber in the group of lines to which said certain brush set has access, and means at said switch for supplying talking current to called subscribers line in said latter group.

18. In an automatic telephone system, telephone lines, call charging devices individual to said lines, an automatic switch for interconnecting said lines, a plurality of brush sets for said switch, each brush set having access to the terminals of a group of said lines, means for selecting any one of said brush sets, means for applying ringing current to a called line, means operative upon the response of called subscribers in certain of said groups of lines for cutting ofl' said ringing current and for preparing the call charging device of the calling line for operation, and means actuated in the selection of a certain brush set for rendering said call charging operating means inoperative and for cutting off said ringing current upon the response of a called subscriber in the group of lines to which said certain brush set has access.

19. In an automatic telephone system, telephone lines, call charging devices individual to said lines, an automatic switch for interconnecting said lines, normally closed talking conductors extending to the. brushes of said switch, a relay actuated in certain selective positions of said switch for interpolating condensers in said conductors, a battery feed relay adapted to be bridged across said conductors on the brush side of said condensers, a slow releasing relay, means for applying ringing current to the called line and for operating the latter relay, and means operative upon the response of the called subscriber when said first relay is operated for operating said second relay thereby deenergizing said slow releasing relay, said second relay and said slow relay cooperating during the releasing period of said slow relay to cut off said ringing current without effecting the operation of the call charging device of the calling line.

20. In an automatic telephone system, telephone lines, call charging devices individual to said lines, an automatic switch for interconnecting said lines, said lines terminating in said switch in groups, means for extending a full metallic circuit through said switch when said switch is operated to select lines in certain groups, means operative over said circuit upon the response of the called subscribers of such groups for preparing the call charging device of the calling line for operation, and means actuated only when sand switch selects a certain group of said lines for interpolating condensers in said circuit for rendering said call charging operating means inoperative upon the response of a called subscriber in the latter group.

In witness whereof, I hereunto subscribe my name this 31st day of May A. 1)., 1923.

PERCY C. SMITH. 

